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In space this week, a satellite flew within a satellite. International Space Station Flight Engineer Jeff Williams "piloted" a unique spacecraft in three dimensions for the first time around the pressurized Destiny module. The demonstration tested the basics of formation flight and autonomous docking that could be useful in future multiple spacecraft formation flying.

That test flight wrapped up a week of experiments, maintenance, spacewalk preparations and packing of equipment set to return to Earth aboard Space Shuttle Discovery following its next mission to the station, targeted for July.

Along with Expedition 13 Commander Pavel Vinogradov, Williams oversaw activities through the 50th day of their planned 180-day mission, focusing on laboratory science experiments in the microgravity science glovebox. That facility hosted the final sample for the Pore Formation and Mobility Investigation experiment, which uses a transparent modeling material to study how bubbles form and migrate during liquid solidification. This is important to understanding the formation of flaws in molten metals as they solidify.

Much of the attention, however, focused on a new experiment flying for the first time on the station ― the Synchronized Position Hold, Engage, Re-orient Experimental Satellites, also known as SPHERES.

Williams, also NASA's station science officer, performed a series of test flights with the first of what eventually will be a constellation of three small free-flying satellites designed to demonstrate the basics of formation flight and autonomous docking.

For the first tests, only one satellite and two beacons ― one mounted and one hand-held ― were used. The satellite is eight inches in diameter and has a mass of about seven pounds. It also contains internal avionics, software and communications systems and is maneuvered using compressed carbon dioxide gas thrusters.

During the first test flight, performed autonomously in Destiny, the satellite made a series of 10-15 pre-planned maneuvers lasting up to 10 minutes each. After Williams selected and loaded the appropriate software on the laptop, the satellite began its pre-programmed maneuvers to test attitude control, station keeping, re-targeting, collision avoidance and fuel balancing.

This technology could be used to design spacecraft constellations or arrays or to develop free-flying robotic assistants to help astronauts on future spacewalks.

NASA's payload operations team at the agency's Marshall Space Flight Center, Huntsville, Ala., coordinates U.S. science activities on the station.

On the maintenance front, Vinogradov prepped for a June 1 space walk by reconfiguring ventilation lines associated with the Elektron oxygen generating system in the Zvezda module. One of the spacewalk tasks will be to install a new external hydrogen vent line for the Elektron. Oxygen is being provided now by storage tanks in the Progress supply vehicle. The Elektron will remain deactivated until after the spacewalk.

Early in the week, the carbon dioxide removal system, known as Vozdukh, in the Russian segment malfunctioned. Flight controllers activated the carbon dioxide removal system in Destiny until troubleshooting restored Vozdukh's operation. Both units will run in tandem until next week when a new gas analyzer is installed in Vozdukh.

On Thursday, the crew talked with school students in Wisconsin's Winter School District about life in space and experiments aboard the station.

The next station status report will be issued on Friday, May 26, or earlier if events warrant. For more about the crew's activities and station sighting opportunities, visit: